With default MPLS behavior, the ingress router pushes a label, transit routers perform label swaps, the penultimate router pops the label (PHP), and the egress router receives the packet without the transport label. In the path R1-R5, R1 pushes the label, R4 performs the pop as the penultimate hop, and R5 is the egress. Therefore, the only router performing purely label swap operations is the intermediate transit router R3.

BGP selects the active route based on an ordered list of attributes. The correct order is:
Weight (Cisco proprietary, not listed in the options)
Local Preference
Network (route) originated from the BGP router itself
Shortest AS Path
Lowest Origin Type
Lowest MED
eBGP over iBGP paths
Closest IGP Neighbor
Lowest Router ID
The next hop is checked for reachability but is not part of the BGP decision process for selecting the best path.

TheBorder Gateway Protocol (BGP)operates based on a strict set of advertisement rules designed to prevent routing loops while ensuring global reachability. These rules differ significantly depending on whether the relationship isExternal BGP (EBGP)orInternal BGP (IBGP).
1. EBGP Advertisement (Option A):In a standard EBGP scenario, a router acts as an exit/entry point for an Autonomous System. When an EBGP speaker receives a valid route from any peer (Internal or External), it will, by default, advertise that route to all of its other EBGP peers. This is the primary mechanism that allows prefixes to propagate across the global internet from one AS to another.
2. IBGP Split Horizon (Option D):
The most critical rule within an AS is theIBGP Split Horizonrule. To prevent loops within an AS, BGP dictates that a route learned from an IBGP peermust notbe advertised to any other IBGP peer. This is why BGP requires a "full mesh" of IBGP sessions or the use ofRoute Reflectorsto ensure all internal routers learn all routes. Without this rule, a route could circulate infinitely within the AS because IBGP does not update the AS_PATH attribute.
3. EBGP to IBGP Propagation (Option B):
When a router learns a route from an EBGP peer, it is permitted to advertise that route to all of its IBGP peers.
This ensures that everyone inside the network knows how to reach external destinations. However, it is important to remember that in Junos OS, theBGP Next Hopis not modified by default when sending routes to IBGP peers, often requiring a "next-hop-self" policy to ensure internal reachability.
Options C and E are incorrect because they directly contradict these fundamental BGP loop-prevention and propagation mechanisms.

IS-IS is a link-state routing protocol that uses a Shortest Path First (SPF) algorithm to create a topology map of the network. It floods link-state advertisements (LSAs) to all nodes within the network area to ensure each node has a consistent view of the network topology.